1. Field of the Invention
The present invention relates to a solid-state image sensing device and a method of fabricating a solid state image sensing device, and especially to those suitable for a Threshold Voltage Modulation Image Sensor (VMIS).
2. Related Art
In conventional solid-state image sensors, CCD sensors having a priority in image quality and CMOS sensors having a priority in low power consumption are commonly used.
Further, in Japanese Unexamined Patent Publication No. 2001-177085, for example, a threshold voltage modulation image sensor is disclosed, which realizes low power consumption equivalent to the CMOS sensors while providing image quality equivalent to the CCD sensors by embedding a light receiving section used for the CCD sensors in the CMOS circuits.
In conventional threshold voltage modulation image sensors, in order to prevent carriers generated in the light-receiving diode area from remaining in the light-receiving diode area without being sent to the carrier pockets, the edge of a floating p-type well in the light-receiving diode area and the edge of a floating p-type well in a field effect transistor for detecting light signals are designed to overlap.
However, if the overlapping section of the edge of the floating p-type well in the light-receiving diode and the edge of the floating p-type well in the field effect transistor for light signal detection is formed, a potential hole is generated in the overlapping section, in which the carrier easily pools.
It is problematic that if the overlapping section of the edge of the floating p-type well in the light-receiving diode area and the edge of the floating p-type well in the field effect transistor for light signal detection is shifted to the light-receiving diode area, the carriers pooled in the overlapping section are not completely swept out to a substrate side to be residual carriers when clearing the carrier pooled in the carrier pocket, which causes residual images.
Therefore, the present invention is intended to provide a solid-state image sensing device and a method of fabricating a solid-state image sensing device capable of reducing the residual carriers in clearing the carriers without preventing the carriers generated in the light-receiving diode area from flowing into the carrier pocket.